Method for a ue for requesting a channel state information reference signal (csi-rs) or a sounding reference signal (srs)

ABSTRACT

Aspects of the disclosure relate to a method of operating a scheduled entity for wireless communication with a network. In some aspects, the scheduled entity transmits a message that requests a scheduling entity to transmit at least one reference signal. The scheduled entity obtains channel state information based on the at least one reference signal. The scheduled entity transmits a report that includes the channel state information. In other aspects, the scheduled entity transmits a message that requests a scheduling entity to schedule a reference signal transmission for the scheduled entity. The scheduled entity obtains an assignment of resources for transmission of the reference signal in response to the message. The scheduled entity transmits the reference signal based on the assignment of resources. Other aspects, embodiments, and features are also claimed and described.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No. 16/192,524entitled “METHOD FOR A UE FOR REQUESTING A CHANNEL STATE INFORMATIONREFERENCE SIGNAL (CSI-RS) OR A SOUNDING REFERENCE SIGNAL (SRS)” filed onNov. 15, 2018, which claims priority to and the benefit of U.S.Provisional Application No. 62/588,273 entitled “METHOD FOR A UE FORREQUESTING A CHANNEL STATE INFORMATION REFERENCE SIGNAL (CSI-RS) OR ASOUNDING REFERENCE SIGNAL (SRS)” filed on Nov. 17, 2017, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The technology described herein relates generally to wirelesscommunication systems, and more particularly, to a method for a userequipment (UE) for requesting a Channel State Information ReferenceSignal (CSI-RS) or a Sounding Reference Signal (SRS).

INTRODUCTION

In conventional wireless communication systems, such as millimeter wave(mmW) cellular systems, a user equipment (UE) and a base station (BS)may use beamforming to overcome high path-losses. In doing so, both theUE and the BS may find at least one adequate beam in order to form alink (also referred to as a beam pair link (BPL)). The UE and BS maymonitor the quality of the BPL and may independently attempt to refinetheir respective beams to maintain or improve the quality of the BPL.

For example, in scenarios where the UE implements multiple-inputmultiple-output (MIMO) communications, the UE may also need to refineits MIMO communication parameters (e.g., modulation and coding scheme(MCS), precoding matrix, etc.) as part of its beam refinement procedure.Such refinement of MIMO communication parameters may require one or moresignals from the BS. Conventional wireless communication systems,however, do not provide mechanisms that enable a UE to request the BS totransmit the one or more signals needed for refinement of MIMOcommunication parameters. As a result, the UE in the previouslydescribed scenarios may not be able to adequately perform the beamrefinement procedures needed to maintain or improve the quality of theBPL.

BRIEF SUMMARY OF SOME EXAMPLES

The following presents a simplified summary of one or more aspects ofthe present disclosure, in order to provide a basic understanding ofsuch aspects. This summary is not an extensive overview of allcontemplated features of the disclosure, and is intended neither toidentify key or critical elements of all aspects of the disclosure norto delineate the scope of any or all aspects of the disclosure. Its solepurpose is to present some concepts of one or more aspects of thedisclosure in a simplified form as a prelude to the more detaileddescription that is presented later.

In one example, a method of wireless communication for a scheduledentity (e.g., a user equipment (UE)) is disclosed. The method includestransmitting a message that requests a scheduling entity (e.g., a basestation (BS)) to transmit at least one reference signal, obtainingchannel state information based on the at least one reference signal,and transmitting a report that includes the channel state information.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes at least one processor, a transceivercommunicatively coupled to the at least one processor, and a memorycommunicatively coupled to the at least one processor. The at least oneprocessor is configured to transmit a message that requests a schedulingentity to transmit at least one reference signal, obtain channel stateinformation based on the at least one reference signal, and transmit areport that includes the channel state information.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes means for transmitting a message that requests ascheduling entity to transmit at least one reference signal, means forobtaining channel state information based on the at least one referencesignal, and means for transmitting a report that includes the channelstate information.

In one example, a non-transitory computer-readable medium storingcomputer-executable code is disclosed. The non-transitorycomputer-readable medium includes code for causing a computer totransmit, from a scheduled entity, a message that requests a schedulingentity to transmit at least one reference signal. The non-transitorycomputer-readable medium further includes code for causing the computerto obtain, at the scheduled entity, channel state information based onthe at least one reference signal. The non-transitory computer-readablemedium further includes code for causing the computer to transmit, fromthe scheduled entity, a report that includes the channel stateinformation.

In one example, a method of wireless communication for a scheduledentity is disclosed. The method includes transmitting, from a scheduledentity, a message that requests a scheduling entity to schedule areference signal transmission for the scheduled entity, obtaining, atthe scheduled entity, an assignment of resources for transmission of thereference signal in response to the message, and transmitting, from thescheduled entity, the reference signal based on the assignment ofresources.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes at least one processor, a transceivercommunicatively coupled to the at least one processor, and a memorycommunicatively coupled to the at least one processor. The at least oneprocessor is configured to transmit a message that requests a schedulingentity to schedule a reference signal transmission for the scheduledentity, obtain an assignment of resources for transmission of thereference signal in response to the message, and transmit the referencesignal based on the assignment of resources.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes means for transmitting a message that requests ascheduling entity to schedule a reference signal transmission for thescheduled entity, means for obtaining an assignment of resources fortransmission of the reference signal in response to the message, andmeans for transmitting the reference signal based on the assignment ofresources.

In one example, a non-transitory computer-readable medium storingcomputer-executable code is disclosed. The non-transitorycomputer-readable medium includes code for causing a computer totransmit, from a scheduled entity, a message that requests a schedulingentity to schedule a reference signal transmission for the scheduledentity. The non-transitory computer-readable medium further includescode for causing the computer to obtain, at the scheduled entity, anassignment of resources for transmission of the reference signal inresponse to the message. The non-transitory computer-readable mediumfurther includes code for causing the computer to transmit, from thescheduled entity, the reference signal based on the assignment ofresources.

In one example, a method of wireless communication for a schedulingentity is disclosed. The method includes obtaining a message thatrequests the scheduling entity to transmit at least one referencesignal, and transmitting the at least one reference signal to ascheduled entity in response to the message.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes at least one processor, a transceivercommunicatively coupled to the at least one processor, and a memorycommunicatively coupled to the at least one processor. The at least oneprocessor is configured to obtain a message that requests the schedulingentity to transmit at least one reference signal, and transmit the atleast one reference signal to a scheduled entity in response to themessage.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes means for obtaining a message that requests thescheduling entity to transmit at least one reference signal, and meansfor transmitting the at least one reference signal to a scheduled entityin response to the message.

In one example, a non-transitory computer-readable medium storingcomputer-executable code is disclosed. The non-transitorycomputer-readable medium includes code for causing a computer to obtain,at a scheduling entity, a message that requests the scheduling entity totransmit at least one reference signal. The non-transitorycomputer-readable medium further includes code for causing the computerto transmit, from the scheduling entity, the at least one referencesignal to a scheduled entity in response to the message.

In one example, a method of wireless communication for a schedulingentity is disclosed. The method includes obtaining a message thatrequests the scheduling entity to schedule a reference signaltransmission for a scheduled entity, transmitting, from the schedulingentity, a first assignment of resources to the scheduled entity fortransmission of the reference signal in response to the message, andobtaining at least one reference signal from the scheduled entity.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes at least one processor, a transceivercommunicatively coupled to the at least one processor, and a memorycommunicatively coupled to the at least one processor. The at least oneprocessor is configured to obtain a message that requests the schedulingentity to schedule a reference signal transmission for a scheduledentity, transmit a first assignment of resources to the scheduled entityfor transmission of the reference signal in response to the message, andobtain at least one reference signal from the scheduled entity.

In one example, an apparatus for wireless communication is disclosed.The apparatus includes means for obtaining a message that requests thescheduling entity to schedule a reference signal transmission for ascheduled entity, means for transmitting a first assignment of resourcesto the scheduled entity for transmission of the reference signal inresponse to the message, and means for obtaining at least one referencesignal from the scheduled entity.

In one example, a non-transitory computer-readable medium storingcomputer-executable code is disclosed. The non-transitorycomputer-readable medium includes code for causing a computer to obtain,at a scheduling entity, a message that requests the scheduling entity toschedule a reference signal transmission for a scheduled entity. Thenon-transitory computer-readable medium further includes code forcausing the computer to transmit, from the scheduling entity, a firstassignment of resources to the scheduled entity for transmission of thereference signal in response to the message. The non-transitorycomputer-readable medium further includes code for causing the computerto obtain, at the scheduling entity, at least one reference signal fromthe scheduled entity.

These and other aspects of the invention will become more fullyunderstood upon a review of the detailed description, which follows.Other aspects, features, and embodiments will become apparent to thoseof ordinary skill in the art, upon reviewing the following descriptionof specific, exemplary embodiments in conjunction with the accompanyingfigures. While features may be discussed relative to certain embodimentsand figures below, all embodiments can include one or more of theadvantageous features discussed herein. In other words, while one ormore embodiments may be discussed as having certain advantageousfeatures, one or more of such features may also be used in accordancewith the various embodiments discussed herein. In similar fashion, whileexemplary embodiments may be discussed below as device, system, ormethod embodiments it should be understood that such exemplaryembodiments can be implemented in various devices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a wireless communication systemaccording to some aspects.

FIG. 2 is a conceptual illustration of an example of a radio accessnetwork according to some aspects.

FIG. 3 is a block diagram illustrating a wireless communication systemsupporting multiple-input multiple-output (MIMO) communication.

FIG. 4 is a block diagram conceptually illustrating an example of ahardware implementation for a scheduling entity according to someaspects of the disclosure.

FIG. 5 is a block diagram conceptually illustrating an example of ahardware implementation for a scheduled entity according to some aspectsof the disclosure.

FIG. 6 is a signal flow diagram according to some aspects of thedisclosure.

FIG. 7 is a signal flow diagram according to some aspects of thedisclosure.

FIG. 8 is a flow chart illustrating an exemplary process according tosome aspects of the disclosure.

FIG. 9 is a flow chart illustrating an exemplary process according tosome aspects of the disclosure.

FIG. 10 is a flow chart illustrating an exemplary process according tosome aspects of the disclosure.

FIG. 11 is a flow chart illustrating an exemplary process according tosome aspects of the disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

The term beamforming may generally refer to a directional signaltransmission or reception. For a beamformed transmission, the amplitudeand phase of each antenna in an array of antennas may be precoded, orcontrolled to create a desired (i.e., directional) pattern ofconstructive and destructive interference in the wavefront.

The term multiple-input multiple-output (MIMO) may generally refer to amulti-antenna technology that exploits multipath signal propagation sothat the information-carrying capacity of a wireless link can bemultiplied by using multiple antennas at the transmitter and receiver tosend multiple simultaneous streams At the multi-antenna transmitter, asuitable precoding algorithm (scaling the respective streams' amplitudeand phase) is applied (in some examples, based on known channel stateinformation). At the multi-antenna receiver, the different spatialsignatures of the respective streams (and, in some examples, knownchannel state information) can enable the separation of these streamsfrom one another. In single-user MIMO, the transmitter sends one or morestreams to the same receiver, taking advantage of capacity gainsassociated with using multiple Tx, Rx antennas in rich scatteringenvironments where channel variations can be tracked. The receiver maytrack these channel variations and provide corresponding feedback to thetransmitter. This feedback may include channel quality information(CQI), the number of preferred data streams (e.g., rate control, a rankindicator (RI)), and a precoding matrix index (PMI).

The term massive MIMO may generally refer to a MIMO system with a verylarge number of antennas (e.g., greater than an 8×8 array).

The term MU-MIMO may generally refer to a multi-antenna technology wherea base station, in communication with a large number of UEs, can exploitmultipath signal propagation to increase overall network capacity byincreasing throughput and spectral efficiency, and reducing the requiredtransmission energy. The transmitter may attempt to increase thecapacity by transmitting to multiple users using its multiple transmitantennas at the same time, and also using the same allocatedtime-frequency resources. The receiver may transmit feedback including aquantized version of the channel so that the transmitter can schedulethe receivers with good channel separation. The transmitted data isprecoded to maximize throughput for users and minimize inter-userinterference.

The various concepts presented throughout this disclosure may beimplemented across a broad variety of telecommunication systems, networkarchitectures, and communication standards. Referring now to FIG. 1, asan illustrative example without limitation, various aspects of thepresent disclosure are illustrated with reference to a wirelesscommunication system 100. The wireless communication system 100 includesthree interacting domains: a core network 102, a radio access network(RAN) 104, and a user equipment (UE) 106 (e.g., including UE 106 a, 106b in FIG. 1). By virtue of the wireless communication system 100, the UE106 may be enabled to carry out data communication with an external datanetwork 110, such as (but not limited to) the Internet.

The RAN 104 may implement any suitable wireless communication technologyor technologies to provide radio access to the UE 106. As one example,the RAN 104 may operate according to 3^(rd) Generation PartnershipProject (3GPP) New Radio (NR) specifications, often referred to as 5G.As another example, the RAN 104 may operate under a hybrid of 5G NR andEvolved Universal Terrestrial Radio Access Network (eUTRAN) standards,often referred to as LTE. The 3GPP refers to this hybrid RAN as anext-generation RAN, or NG-RAN. Of course, many other examples may beutilized within the scope of the present disclosure.

As illustrated, the RAN 104 includes a plurality of base stations 108.Broadly, a base station is a network element in a radio access networkresponsible for radio transmission and reception in one or more cells toor from a UE. In different technologies, standards, or contexts, a basestation may variously be referred to by those skilled in the art as abase transceiver station (BTS), a radio base station, a radiotransceiver, a transceiver function, a basic service set (BSS), anextended service set (ESS), an access point (AP), a Node B (NB), aneNode B (eNB), a gNode B (gNB), or some other suitable terminology.

The radio access network 104 is further illustrated supporting wirelesscommunication for multiple mobile apparatuses. A mobile apparatus may bereferred to as user equipment (UE) in 3GPP standards, but may also bereferred to by those skilled in the art as a mobile station (MS), asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal (AT), a mobile terminal, a wireless terminal, a remoteterminal, a handset, a terminal, a user agent, a mobile client, aclient, or some other suitable terminology. A UE may be an apparatus(e.g., a mobile apparatus) that provides a user with access to networkservices.

Within the present document, a “mobile” apparatus need not necessarilyhave a capability to move, and may be stationary. The term mobileapparatus or mobile device broadly refers to a diverse array of devicesand technologies. UEs may include a number of hardware structuralcomponents sized, shaped, and arranged to help in communication; suchcomponents can include antennas, antenna arrays, RF chains, amplifiers,one or more processors, etc. electrically coupled to each other. Forexample, some non-limiting examples of a mobile apparatus include amobile, a cellular (cell) phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a personal computer (PC), a notebook, anetbook, a smartbook, a tablet, a personal digital assistant (PDA), anda broad array of embedded systems, e.g., corresponding to an “Internetof things” (IoT). A mobile apparatus may additionally be an automotiveor other transportation vehicle, a remote sensor or actuator, a robot orrobotics device, a satellite radio, a global positioning system (GPS)device, an object tracking device, a drone, a multi-copter, aquad-copter, a remote control device, a consumer and/or wearable device,such as eyewear, a wearable camera, a virtual reality device, a smartwatch, a health or fitness tracker, a digital audio player (e.g., MP3player), a camera, a game console, etc. A mobile apparatus mayadditionally be a digital home or smart home device such as a homeaudio, video, and/or multimedia device, an appliance, a vending machine,intelligent lighting, a home security system, a smart meter, etc. Amobile apparatus may additionally be a smart energy device, a securitydevice, a solar panel or solar array, a municipal infrastructure devicecontrolling electric power (e.g., a smart grid), lighting, water, etc.;an industrial automation and enterprise device; a logistics controller;agricultural equipment; military defense equipment, vehicles, aircraft,ships, and weaponry, etc. Still further, a mobile apparatus may providefor connected medicine or telemedicine support, e.g., health care at adistance. Telehealth devices may include telehealth monitoring devicesand telehealth administration devices, whose communication may be givenpreferential treatment or prioritized access over other types ofinformation, e.g., in terms of prioritized access for transport ofcritical service data, and/or relevant QoS for transport of criticalservice data.

Wireless communication between a RAN 104 and a UE 106 may be describedas utilizing an air interface. Transmissions over the air interface froma base station (e.g., base station 108) to one or more UEs (e.g., UE106) may be referred to as downlink (DL) transmission. In accordancewith certain aspects of the present disclosure, the term downlink mayrefer to a point-to-multipoint transmission originating at a schedulingentity (described further below; e.g., base station 108). Another way todescribe this scheme may be to use the term broadcast channelmultiplexing. Transmissions from a UE (e.g., UE 106) to a base station(e.g., base station 108) may be referred to as uplink (UL)transmissions. In accordance with further aspects of the presentdisclosure, the term uplink may refer to a point-to-point transmissionoriginating at a scheduled entity (described further below; e.g., UE106).

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station 108) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more scheduledentities. That is, for scheduled communication, UEs 106, which may bescheduled entities, may utilize resources allocated by the schedulingentity 108.

Base stations 108 are not the only entities that may function asscheduling entities. That is, in some examples, a UE may function as ascheduling entity, scheduling resources for one or more scheduledentities (e.g., one or more other UEs).

As illustrated in FIG. 1, a scheduling entity 108 may broadcast downlinktraffic 112 to one or more scheduled entities 106. Broadly, thescheduling entity 108 is a node or device responsible for schedulingtraffic in a wireless communication network, including the downlinktraffic 112 and, in some examples, uplink traffic 116 from one or morescheduled entities 106 to the scheduling entity 108. On the other hand,the scheduled entity 106 is a node or device that receives downlinkcontrol information 114, including but not limited to schedulinginformation (e.g., a grant), synchronization or timing information, orother control information from another entity in the wirelesscommunication network such as the scheduling entity 108.

In some examples, the UEs such as a first UE 106 a and a second UE 106 bmay utilize sidelink signals for direct D2D communication. Sidelinksignals may include sidelink traffic 122 and sidelink control 124. Thesidelink control 124 may in some examples include a request signal, suchas a request-to-send (RTS), a source transmit signal (STS), and/or adirection selection signal (DSS). The request signal may provide for theUE 106 to request a duration of time to keep a sidelink channelavailable for a sidelink signal. The sidelink control 124 may furtherinclude a response signal, such as a clear-to-send (CTS) and/or adestination receive signal (DRS). The response signal may provide forthe UE 106 to indicate the availability of the sidelink channel, e.g.,for a requested duration of time. An exchange of request and responsesignals (e.g., handshake) may enable different UEs performing sidelinkcommunications to negotiate the availability of the sidelink channelprior to communication of the sidelink traffic 122.

In general, base stations 108 may include a backhaul interface forcommunication with a backhaul portion 120 of the wireless communicationsystem. The backhaul 120 may provide a link between a base station 108and the core network 102. Further, in some examples, a backhaul networkmay provide interconnection between the respective base stations 108.Various types of backhaul interfaces may be employed, such as a directphysical connection, a virtual network, or the like using any suitabletransport network.

The core network 102 may be a part of the wireless communication system100, and may be independent of the radio access technology used in theRAN 104. In some examples, the core network 102 may be configuredaccording to 5G standards (e.g., 5GC). In other examples, the corenetwork 102 may be configured according to a 4G evolved packet core(EPC), or any other suitable standard or configuration.

Referring now to FIG. 2, by way of example and without limitation, aschematic illustration of a RAN 200 is provided. In some examples, theRAN 200 may be the same as the RAN 104 described above and illustratedin FIG. 1. The geographic area covered by the RAN 200 may be dividedinto cellular regions (cells) that can be uniquely identified by a userequipment (UE) based on an identification broadcasted from one accesspoint or base station. FIG. 2 illustrates macrocells 202, 204, and 206,and a small cell 208, each of which may include one or more sectors (notshown). A sector is a sub-area of a cell. All sectors within one cellare served by the same base station. A radio link within a sector can beidentified by a single logical identification belonging to that sector.In a cell that is divided into sectors, the multiple sectors within acell can be formed by groups of antennas with each antenna responsiblefor communication with UEs in a portion of the cell.

In FIG. 2, two base stations 210 and 212 are shown in cells 202 and 204;and a third base station 214 is shown controlling a remote radio head(RRH) 216 in cell 206. That is, a base station can have an integratedantenna or can be connected to an antenna or RRH by feeder cables. Inthe illustrated example, the cells 202, 204, and 126 may be referred toas macrocells, as the base stations 210, 212, and 214 support cellshaving a large size. Further, a base station 218 is shown in the smallcell 208 (e.g., a microcell, picocell, femtocell, home base station,home Node B, home eNode B, etc.) which may overlap with one or moremacrocells. In this example, the cell 208 may be referred to as a smallcell, as the base station 218 supports a cell having a relatively smallsize. Cell sizing can be done according to system design as well ascomponent constraints.

It is to be understood that the radio access network 200 may include anynumber of wireless base stations and cells. Further, a relay node may bedeployed to extend the size or coverage area of a given cell. The basestations 210, 212, 214, 218 provide wireless access points to a corenetwork for any number of mobile apparatuses. In some examples, the basestations 210, 212, 214, and/or 218 may be the same as the basestation/scheduling entity 108 described above and illustrated in FIG. 1.

FIG. 2 further includes a quadcopter or drone 220, which may beconfigured to function as a base station. That is, in some examples, acell may not necessarily be stationary, and the geographic area of thecell may move according to the location of a mobile base station such asthe quadcopter 220.

Within the RAN 200, the cells may include UEs that may be incommunication with one or more sectors of each cell. Further, each basestation 210, 212, 214, 218, and 220 may be configured to provide anaccess point to a core network 102 (see FIG. 1) for all the UEs in therespective cells. For example, UEs 222 and 224 may be in communicationwith base station 210; UEs 226 and 228 may be in communication with basestation 212; UEs 230 and 232 may be in communication with base station214 by way of RRH 216; UE 234 may be in communication with base station218; and UE 236 may be in communication with mobile base station 220. Insome examples, the UEs 222, 224, 226, 228, 230, 232, 234, 236, 238, 240,and/or 242 may be the same as the UE/scheduled entity 106 describedabove and illustrated in FIG. 1.

In some examples, a mobile network node (e.g., quadcopter 220) may beconfigured to function as a UE. For example, the quadcopter 220 mayoperate within cell 202 by communicating with base station 210.

In a further aspect of the RAN 200, sidelink signals may be used betweenUEs without necessarily relying on scheduling or control informationfrom a base station. For example, two or more UEs (e.g., UEs 226 and228) may communicate with each other using peer to peer (P2P) orsidelink signals 227 without relaying that communication through a basestation (e.g., base station 212). In a further example, UE 238 isillustrated communicating with UEs 240 and 242. Here, the UE 238 mayfunction as a scheduling entity or a primary sidelink device, and UEs240 and 242 may function as a scheduled entity or a non-primary (e.g.,secondary) sidelink device. In still another example, a UE may functionas a scheduling entity in a device-to-device (D2D), peer-to-peer (P2P),or vehicle-to-vehicle (V2V) network, and/or in a mesh network. In a meshnetwork example, UEs 240 and 242 may optionally communicate directlywith one another in addition to communicating with the scheduling entity238. Thus, in a wireless communication system with scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, or a mesh configuration, a scheduling entity and one ormore scheduled entities may communicate utilizing the scheduledresources.

In the radio access network 200, the ability for a UE to communicatewhile moving, independent of its location, is referred to as mobility.The various physical channels between the UE and the radio accessnetwork are generally set up, maintained, and released under the controlof an access and mobility management function (AMF, not illustrated,part of the core network 102 in FIG. 1), which may include a securitycontext management function (SCMF) that manages the security context forboth the control plane and the user plane functionality, and a securityanchor function (SEAF) that performs authentication.

In various aspects of the disclosure, a radio access network 200 mayutilize DL-based mobility or UL-based mobility to enable mobility andhandovers (i.e., the transfer of a UE's connection from one radiochannel to another). In a network configured for DL-based mobility,during a call with a scheduling entity, or at any other time, a UE maymonitor various parameters of the signal from its serving cell as wellas various parameters of neighboring cells. Depending on the quality ofthese parameters, the UE may maintain communication with one or more ofthe neighboring cells. During this time, if the UE moves from one cellto another, or if signal quality from a neighboring cell exceeds thatfrom the serving cell for a given amount of time, the UE may undertake ahandoff or handover from the serving cell to the neighboring (target)cell. For example, UE 224 (illustrated as a vehicle, although anysuitable form of UE may be used) may move from the geographic areacorresponding to its serving cell 202 to the geographic areacorresponding to a neighbor cell 206. When the signal strength orquality from the neighbor cell 206 exceeds that of its serving cell 202for a given amount of time, the UE 224 may transmit a reporting messageto its serving base station 210 indicating this condition. In response,the UE 224 may receive a handover command, and the UE may undergo ahandover to the cell 206.

In a network configured for UL-based mobility, UL reference signals fromeach UE may be utilized by the network to select a serving cell for eachUE. In some examples, the base stations 210, 212, and 214/216 maybroadcast unified synchronization signals (e.g., unified PrimarySynchronization Signals (PSSs), unified Secondary SynchronizationSignals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs222, 224, 226, 228, 230, and 232 may receive the unified synchronizationsignals, derive the carrier frequency and slot timing from thesynchronization signals, and in response to deriving timing, transmit anuplink pilot or reference signal. The uplink pilot signal transmitted bya UE (e.g., UE 224) may be concurrently received by two or more cells(e.g., base stations 210 and 214/216) within the radio access network200. Each of the cells may measure a strength of the pilot signal, andthe radio access network (e.g., one or more of the base stations 210 and214/216 and/or a central node within the core network) may determine aserving cell for the UE 224. As the UE 224 moves through the radioaccess network 200, the network may continue to monitor the uplink pilotsignal transmitted by the UE 224. When the signal strength or quality ofthe pilot signal measured by a neighboring cell exceeds that of thesignal strength or quality measured by the serving cell, the network 200may handover the UE 224 from the serving cell to the neighboring cell,with or without informing the UE 224.

Although the synchronization signal transmitted by the base stations210, 212, and 214/216 may be unified, the synchronization signal may notidentify a particular cell, but rather may identify a zone of multiplecells operating on the same frequency and/or with the same timing. Theuse of zones in 5G networks or other next generation communicationnetworks enables the uplink-based mobility framework and improves theefficiency of both the UE and the network, since the number of mobilitymessages that need to be exchanged between the UE and the network may bereduced.

In various implementations, the air interface in the radio accessnetwork 200 may utilize licensed spectrum, unlicensed spectrum, orshared spectrum. Licensed spectrum provides for exclusive use of aportion of the spectrum, generally by virtue of a mobile networkoperator purchasing a license from a government regulatory body.Unlicensed spectrum provides for shared use of a portion of the spectrumwithout need for a government-granted license. While compliance withsome technical rules is generally still required to access unlicensedspectrum, generally, any operator or device may gain access. Sharedspectrum may fall between licensed and unlicensed spectrum, whereintechnical rules or limitations may be required to access the spectrum,but the spectrum may still be shared by multiple operators and/ormultiple RATs. For example, the holder of a license for a portion oflicensed spectrum may provide licensed shared access (LSA) to share thatspectrum with other parties, e.g., with suitable licensee-determinedconditions to gain access.

The air interface in the radio access network 200 may utilize one ormore duplexing algorithms. Duplex refers to a point-to-pointcommunication link where both endpoints can communicate with one anotherin both directions. Full duplex means both endpoints can simultaneouslycommunicate with one another. Half duplex means only one endpoint cansend information to the other at a time. In a wireless link, a fullduplex channel generally relies on physical isolation of a transmitterand receiver, and suitable interference cancellation technologies. Fullduplex emulation is frequently implemented for wireless links byutilizing frequency division duplex (FDD) or time division duplex (TDD).In FDD, transmissions in different directions operate at differentcarrier frequencies. In TDD, transmissions in different directions on agiven channel are separated from one another using time divisionmultiplexing. That is, at some times the channel is dedicated fortransmissions in one direction, while at other times the channel isdedicated for transmissions in the other direction, where the directionmay change very rapidly, e.g., several times per slot.

In some aspects of the disclosure, the scheduling entity and/orscheduled entity may be configured for beamforming and/or multiple-inputmultiple-output (MIMO) technology. FIG. 3 illustrates an example of awireless communication system 300 supporting MIMO. In a MIMO system, atransmitter 302 includes multiple transmit antennas 304 (e.g., Ntransmit antennas) and a receiver 306 includes multiple receive antennas308 (e.g., M receive antennas). Thus, there are N×M signal paths 310from the transmit antennas 304 to the receive antennas 308. Each of thetransmitter 302 and the receiver 306 may be implemented, for example,within a scheduling entity 108, a scheduled entity 106, or any othersuitable wireless communication device.

The use of such multiple antenna technology enables the wirelesscommunication system to exploit the spatial domain to support spatialmultiplexing, beamforming, and transmit diversity. Spatial multiplexingmay be used to transmit different streams of data, also referred to aslayers, simultaneously on the same time-frequency resource. The datastreams may be transmitted to a single UE to increase the data rate orto multiple UEs to increase the overall system capacity, the latterbeing referred to as multi-user MIMO (MU-MIMO). This is achieved byspatially precoding each data stream (i.e., multiplying the data streamswith different weighting and phase shifting) and then transmitting eachspatially precoded stream through multiple transmit antennas on thedownlink The spatially precoded data streams arrive at the UE(s) withdifferent spatial signatures, which enables each of the UE(s) to recoverthe one or more data streams destined for that UE. On the uplink, eachUE transmits a spatially precoded data stream, which enables the basestation to identify the source of each spatially precoded data stream.

The number of data streams or layers corresponds to the rank of thetransmission. In general, the rank of the MIMO system 300 is limited bythe number of transmit or receive antennas 304 or 308, whichever islower. In addition, the channel conditions at the UE, as well as otherconsiderations, such as the available resources at the base station, mayalso affect the transmission rank. For example, the rank (and therefore,the number of data streams) assigned to a particular UE on the downlinkmay be determined based on the rank indicator (RI) transmitted from theUE to the base station. The RI may be determined based on the antennaconfiguration (e.g., the number of transmit and receive antennas) and ameasured signal-to-interference-and-noise ratio (SINR) on each of thereceive antennas. The RI may indicate, for example, the number of layersthat may be supported under the current channel conditions. The basestation may use the RI, along with resource information (e.g., theavailable resources and amount of data to be scheduled for the UE), toassign a transmission rank to the UE.

In Time Division Duplex (TDD) systems, the UL and DL are reciprocal, inthat each uses different time slots of the same frequency bandwidth.Therefore, in TDD systems, the base station may assign the rank for DLMIMO transmissions based on UL SINR measurements (e.g., based on aSounding Reference Signal (SRS) transmitted from the UE or other pilotsignal). Based on the assigned rank, the base station may then transmitthe CSI-RS with separate C-RS sequences for each layer to provide formulti-layer channel estimation. From the CSI-RS, the UE may measure thechannel quality across layers and resource blocks and feed back the CQIand RI values to the base station for use in updating the rank andassigning REs for future downlink transmissions.

In the simplest case, as shown in FIG. 3, a rank-2 spatial multiplexingtransmission on a 2×2 MIMO antenna configuration will transmit one datastream from each transmit antenna 304. Each data stream reaches eachreceive antenna 308 along a different signal path 310. The receiver 306may then reconstruct the data streams using the received signals fromeach receive antenna 308.

In order for transmissions over the radio access network 200 to obtain alow block error rate (BLER) while still achieving very high data rates,channel coding may be used. That is, wireless communication maygenerally utilize a suitable error correcting block code. In a typicalblock code, an information message or sequence is split up into codeblocks (CBs), and an encoder (e.g., a CODEC) at the transmitting devicethen mathematically adds redundancy to the information message.Exploitation of this redundancy in the encoded information message canimprove the reliability of the message, enabling correction for any biterrors that may occur due to the noise.

In early 5G NR specifications, user data is coded using quasi-cycliclow-density parity check (LDPC) with two different base graphs: one basegraph is used for large code blocks and/or high code rates, while theother base graph is used otherwise. Control information and the physicalbroadcast channel (PBCH) are coded using Polar coding, based on nestedsequences. For these channels, puncturing, shortening, and repetitionare used for rate matching.

However, those of ordinary skill in the art will understand that aspectsof the present disclosure may be implemented utilizing any suitablechannel code. Various implementations of scheduling entities 108 andscheduled entities 106 may include suitable hardware and capabilities(e.g., an encoder, a decoder, and/or a CODEC) to utilize one or more ofthese channel codes for wireless communication.

The air interface in the radio access network 200 may utilize one ormore multiplexing and multiple access algorithms to enable simultaneouscommunication of the various devices. For example, 5G NR specificationsprovide multiple access for UL transmissions from UEs 222 and 224 tobase station 210, and for multiplexing for DL transmissions from basestation 210 to one or more UEs 222 and 224, utilizing orthogonalfrequency division multiplexing (OFDM) with a cyclic prefix (CP). Inaddition, for UL transmissions, 5G NR specifications provide support fordiscrete Fourier transform-spread-OFDM (DFT-s-OFDM) with a CP (alsoreferred to as single-carrier FDMA (SC-FDMA)). However, within the scopeof the present disclosure, multiplexing and multiple access are notlimited to the above schemes, and may be provided utilizing timedivision multiple access (TDMA), code division multiple access (CDMA),frequency division multiple access (FDMA), sparse code multiple access(SCMA), resource spread multiple access (RSMA), or other suitablemultiple access schemes. Further, multiplexing DL transmissions from thebase station 210 to UEs 222 and 224 may be provided utilizing timedivision multiplexing (TDM), code division multiplexing (CDM), frequencydivision multiplexing (FDM), orthogonal frequency division multiplexing(OFDM), sparse code multiplexing (SCM), or other suitable multiplexingschemes.

FIG. 4 is a block diagram illustrating an example of a hardwareimplementation for a scheduling entity 400 employing a processing system414. For example, the scheduling entity may be a base station asillustrated in any one or more of FIGS. 1, 2, and/or 3.

The scheduling entity 400 may be implemented with a processing system414 that includes one or more processors 404. Examples of processors 404include microprocessors, microcontrollers, digital signal processors(DSPs), field programmable gate arrays (FPGAs), programmable logicdevices (PLDs), state machines, gated logic, discrete hardware circuits,and other suitable hardware configured to perform the variousfunctionality described throughout this disclosure. In various examples,the scheduling entity 400 may be configured to perform any one or moreof the functions described herein. That is, the processor 404, asutilized in a scheduling entity 400, may be used to implement any one ormore of the processes and procedures described below and illustrated inFIGS. 10 and/or 11.

In this example, the processing system 414 may be implemented with a busarchitecture, represented generally by the bus 402. The bus 402 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 414 and the overall designconstraints. The bus 402 communicatively couples together variouscircuits including one or more processors (represented generally by theprocessor 404), a memory 405, and computer-readable media (representedgenerally by the computer-readable medium 406). The bus 402 may alsolink various other circuits such as timing sources, peripherals, voltageregulators, and power management circuits, which are well known in theart, and therefore, will not be described any further. A bus interface408 provides an interface between the bus 402 and a transceiver 410. Thetransceiver 410 provides a communication interface or means forcommunicating with various other apparatus over a transmission medium.Depending upon the nature of the apparatus, a user interface 412 (e.g.,keypad, display, speaker, microphone, joystick) may also be provided.

In some aspects of the disclosure, the processor 404 may include arequest obtaining circuit 440 configured for various functions,including, for example, obtaining a message that requests the schedulingentity to transmit at least one reference signal and/or obtaining amessage that requests the scheduling entity to schedule a referencesignal transmission for a scheduled entity. For example, the requestobtaining circuit 440 may be configured to implement one or more of thefunctions described below in relation to FIGS. 10 and/or 11, including,e.g., blocks 1002, 1102.

In some aspects of the disclosure, the processor 404 may include areference signal transmitting and obtaining circuit 442 configured forvarious functions, including, for example, transmitting at least onereference signal to a scheduled entity in response to the message and/orobtaining at least one reference signal from the scheduled entity. Forexample, the reference signal transmitting and obtaining circuit 442 maybe configured to implement one or more of the functions described belowin relation to FIGS. 10 and/or 11, including, e.g., blocks 1004, 1106.

In some aspects of the disclosure, the processor 404 may include areport obtaining circuit 444 configured for various functions,including, for example, obtaining a report including channel stateinformation from the scheduled entity, wherein the channel stateinformation is based on at least one reference signal. For example, thereport obtaining circuit 444 may be configured to implement one or moreof the functions described below in relation to FIG. 10, including,e.g., block 1006.

In some aspects of the disclosure, the processor 404 may include aresource assignment transmitting circuit 446 configured for variousfunctions, including, for example, transmitting a first assignment ofresources to the scheduled entity for transmission of the referencesignal in response to the message and/or transmitting, from thescheduling entity, a second assignment of resources to the scheduledentity for an uplink data transmission in a MIMO transmission mode,wherein the resources are assigned based on the channel stateinformation. For example, the resource assignment transmitting circuit446 may be configured to implement one or more of the functionsdescribed below in relation to FIG. 11, including, e.g., blocks 1104and/or 1110.

In some aspects of the disclosure, the processor 404 may include a datatransmitting circuit 448 configured for various functions, including,for example, transmitting data based on at least the channel stateinformation. For example, the data transmitting circuit 448 may beconfigured to implement one or more of the functions described below inrelation to FIG. 10, including, e.g., block 1008.

In some aspects of the disclosure, the processor 404 may include achannel state information obtaining circuit 450 configured for variousfunctions, including, for example, obtaining channel state informationbased on the at least one reference signal from the scheduled entity.For example, the channel state information obtaining circuit 450 may beconfigured to implement one or more of the functions described below inrelation to FIG. 11, including, e.g., block 1108.

The processor 404 is responsible for managing the bus 402 and generalprocessing, including the execution of software stored on thecomputer-readable medium 406. The software, when executed by theprocessor 404, causes the processing system 414 to perform the variousfunctions described below for any particular apparatus. Thecomputer-readable medium 406 and the memory 405 may also be used forstoring data that is manipulated by the processor 404 when executingsoftware.

One or more processors 404 in the processing system may executesoftware. Software shall be construed broadly to mean instructions,instruction sets, code, code segments, program code, programs,subprograms, software modules, applications, software applications,software packages, routines, subroutines, objects, executables, threadsof execution, procedures, functions, etc., whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. The software may reside on a computer-readablemedium 406. The computer-readable medium 406 may be a non-transitorycomputer-readable medium. A non-transitory computer-readable mediumincludes, by way of example, a magnetic storage device (e.g., hard disk,floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD)or a digital versatile disc (DVD)), a smart card, a flash memory device(e.g., a card, a stick, or a key drive), a random access memory (RAM), aread only memory (ROM), a programmable ROM (PROM), an erasable PROM(EPROM), an electrically erasable PROM (EEPROM), a register, a removabledisk, and any other suitable medium for storing software and/orinstructions that may be accessed and read by a computer. Thecomputer-readable medium 406 may reside in the processing system 414,external to the processing system 414, or distributed across multipleentities including the processing system 414. The computer-readablemedium 406 may be embodied in a computer program product. By way ofexample, a computer program product may include a computer-readablemedium in packaging materials. Those skilled in the art will recognizehow best to implement the described functionality presented throughoutthis disclosure depending on the particular application and the overalldesign constraints imposed on the overall system.

In one or more examples, the computer-readable storage medium 406 mayinclude request obtaining software 460 configured for various functions,including, for example, obtaining a message that requests the schedulingentity to transmit at least one reference signal and/or obtaining amessage that requests the scheduling entity to schedule a referencesignal transmission for a scheduled entity. For example, the requestobtaining software 460 may be configured to implement one or more of thefunctions described above in relation to FIGS. 10 and/or 11, including,e.g., blocks 1002, 1102.

In one or more examples, the computer-readable storage medium 406 mayinclude reference signal transmitting and obtaining software 462configured for various functions, including, for example, transmittingat least one reference signal to a scheduled entity in response to themessage and/or obtaining at least one reference signal from thescheduled entity. For example, the reference signal transmitting andobtaining software 462 may be configured to implement one or more of thefunctions described above in relation to FIGS. 10 and/or 11, including,e.g., blocks 1004, 1106.

In one or more examples, the computer-readable storage medium 406 mayinclude report obtaining software 464 configured for various functions,including, for example, obtaining a report including channel stateinformation from the scheduled entity, wherein the channel stateinformation is based on at least one reference signal. For example, thereport obtaining software 464 may be configured to implement one or moreof the functions described above in relation to FIG. 10, including,e.g., block 1006.

In one or more examples, the computer-readable storage medium 406 mayinclude resource assignment transmitting software 466 configured forvarious functions, including, for example, transmitting a firstassignment of resources to the scheduled entity for transmission of thereference signal in response to the message and/or transmitting, fromthe scheduling entity, a second assignment of resources to the scheduledentity for an uplink data transmission in a MIMO transmission mode,wherein the resources are assigned based on the channel stateinformation. For example, the resource assignment transmitting software466 may be configured to implement one or more of the functionsdescribed above in relation to FIG. 11, including, e.g., blocks 1104and/or 1110.

In one or more examples, the computer-readable storage medium 406 mayinclude data transmitting software 468 configured for various functions,including, for example, transmitting data based on at least the channelstate information. For example, the data transmitting software 468 maybe configured to implement one or more of the functions described abovein relation to FIG. 10, including, e.g., block 1008.

In one or more examples, the computer-readable storage medium 406 mayinclude channel state information obtaining software 470 configured forvarious functions, including, for example, obtaining channel stateinformation based on the at least one reference signal from thescheduled entity. For example, the channel state information obtainingsoftware 470 may be configured to implement one or more of the functionsdescribed above in relation to FIG. 11, including, e.g., block 1108.

FIG. 5 is a conceptual diagram illustrating an example of a hardwareimplementation for an exemplary scheduled entity 500 employing aprocessing system 514. In accordance with various aspects of thedisclosure, an element, or any portion of an element, or any combinationof elements may be implemented with a processing system 514 thatincludes one or more processors 504. For example, the scheduled entity500 may be a user equipment (UE) as illustrated in any one or more ofFIGS. 1, 2, and/or 3.

The processing system 514 may be substantially the same as theprocessing system 414 illustrated in FIG. 4, including a bus interface508, a bus 502, memory 505, a processor 504, and a computer-readablemedium 506. Furthermore, the scheduled entity 500 may include a userinterface 512 and a transceiver 510 substantially similar to thosedescribed above in FIG. 4. That is, the processor 504, as utilized in ascheduled entity 500, may be used to implement any one or more of theprocesses described below and illustrated in FIGS. 8 and/or 9.

In some aspects of the disclosure, the processor 504 may include arequest transmitting circuit 540 configured for various functions,including, for example, transmitting a message that requests ascheduling entity to transmit at least one reference signal and/ortransmitting a message that requests a scheduling entity to schedule areference signal transmission for the scheduled entity. For example, therequest transmitting circuit 540 may be configured to implement one ormore of the functions described below in relation to FIGS. 8 and/or 9,including, e.g., blocks 804, 904.

In some aspects of the disclosure, the processor 504 may include achannel state information obtaining circuit 542 configured for variousfunctions, including, for example, obtaining channel state informationbased on the at least one reference signal. For example, the channelstate information obtaining circuit 542 may be configured to implementone or more of the functions described below in relation to FIG. 8,including, e.g., block 806.

In some aspects of the disclosure, the processor 506 may include areport transmitting circuit 544 configured for various functions,including, for example, transmitting a report that includes the channelstate information. For example, the report transmitting circuit 544 maybe configured to implement one or more of the functions described belowin relation to FIG. 8, including, e.g., block 808.

In some aspects of the disclosure, the processor 506 may include aresource assignment obtaining circuit 546 configured for variousfunctions, including, for example, obtaining an assignment of resourcesfor transmission of the reference signal in response to the message. Forexample, the resource assignment obtaining circuit 546 may be configuredto implement one or more of the functions described below in relation toFIG. 9, including, e.g., block 906.

In some aspects of the disclosure, the processor 506 may include areference signal transmitting circuit 548 configured for variousfunctions, including, for example, transmitting the reference signalbased on the assignment of resources. For example, the reference signaltransmitting circuit 548 may be configured to implement one or more ofthe functions described below in relation to FIG. 9, including, e.g.,block 908.

In some aspects of the disclosure, the processor 506 may include atransmission quality estimating circuit 550 configured for variousfunctions, including, for example, estimating an amount of improvementin a quality of a downlink data transmission to be gained from thetransmission of the reference signal, wherein the estimated amount ofimprovement is included in the message. In some examples, thetransmission quality estimating circuit 550 may be further configuredfor various functions, including, for example, estimating an amount ofimprovement in a quality of an uplink data transmission to be gainedfrom the transmission of the reference signal, wherein the estimatedamount of improvement is included in the message. For example, thetransmission quality estimating circuit 550 may be configured toimplement one or more of the functions described below in relation toFIGS. 8 and/or 9, including, e.g., blocks 802, 902.

In one or more examples, the computer-readable storage medium 506 mayinclude request transmitting software 560 configured for variousfunctions, including, for example, transmitting a message that requestsa scheduling entity to transmit at least one reference signal and/ortransmitting a message that requests a scheduling entity to schedule areference signal transmission for the scheduled entity. For example, therequest transmitting software 560 may be configured to implement one ormore of the functions described above in relation to FIGS. 8 and/or 9,including, e.g., blocks 804, 904.

In one or more examples, the computer-readable storage medium 506 mayinclude channel state information obtaining software 562 configured forvarious functions, including, for example, obtaining channel stateinformation based on the at least one reference signal. For example, thechannel state information obtaining software 562 may be configured toimplement one or more of the functions described above in relation toFIG. 8, including, e.g., block 806.

In one or more examples, the computer-readable storage medium 506 mayinclude report transmitting software 564 configured for variousfunctions, including, for example, transmitting a report that includesthe channel state information. For example, the report transmittingsoftware 564 may be configured to implement one or more of the functionsdescribed above in relation to FIG. 8, including, e.g., block 808.

In one or more examples, the computer-readable storage medium 506 mayinclude resource assignment obtaining software 566 configured forvarious functions, including, for example, obtaining an assignment ofresources for transmission of the reference signal in response to themessage. For example, the resource assignment obtaining software 566 maybe configured to implement one or more of the functions described abovein relation to FIG. 9, including, e.g., block 906.

In one or more examples, the computer-readable storage medium 506 mayinclude reference signal transmitting software 568 configured forvarious functions, including, for example, transmitting the referencesignal based on the assignment of resources. For example, the referencesignal transmitting software 568 may be configured to implement one ormore of the functions described above in relation to FIG. 9, including,e.g., block 908.

In one or more examples, the computer-readable storage medium 506 mayinclude transmission quality estimating software 570 configured forvarious functions, including, for example, estimating an amount ofimprovement in a quality of a downlink data transmission to be gainedfrom the transmission of the reference signal, wherein the estimatedamount of improvement is included in the message. In some examples, thetransmission quality estimating software 570 may be further configuredfor various functions, including, for example, estimating an amount ofimprovement in a quality of an uplink data transmission to be gainedfrom the transmission of the reference signal, wherein the estimatedamount of improvement is included in the message. For example, thetransmission quality estimating software 570 may be configured toimplement one or more of the functions described above in relation toFIGS. 8 and/or 9, including, e.g., blocks 802, 902.

Downlink Communications

In millimeter wave (mmW) cellular systems, beamforming may be used toovercome high path-losses. To utilize beamforming, both a base stationand a UE may find at least one adequate beam in order to form a link Abeam formed by the base station and a corresponding beam formed by theUE may form what is known as a beam pair link (BPL). The performance ofthe beam pair link may be subject to fading due to Doppler spread orblocking of the signal transmission path. In conventional systems, abase station and a UE typically work with pools of one or more beam pairlinks for the transmission of data and control messages in the downlinkand the uplink The UE and the base station may monitor the quality of abeam pair link and may carry out adjustments, such as beam refinementsat the UE and beam refinements at the base station. In some scenarios,the UE may also have to switch between antenna subarrays. For example,if the UE is moved, its orientation is changed, or an antenna subarraybeing used is blocked by a body part of the user or an object, the UEmay switch to a different antenna subarray.

In downlink communications, data may be transferred from a base stationto a UE using MIMO transmissions as previously discussed with referenceto FIG. 3. For example, MIMO transmissions may enable multiplexing ordiversity gains. Prior to transmitting data on the downlink using MIMOtransmissions, the base station may transmit a channel state informationreference signal (CSI-RS) to the UE using antenna ports associated withone or more beams and/or multiple polarizations. The CSI-RS may enablethe UE to acquire the channel and to measure the channel. For example,in 5G wireless communication network, the CSI-RS may be referred to as aCSI-RS for channel acquisition. The UE may receive the CSI-RS and maydetermine channel state information (CSI). For example, the CSI mayinclude the modulation and coding scheme (MCS), rank indication (RI),and/or precoding matrix indication (PMI) for a MIMO transmission. The UEmay report the CSI to the base station, which may use the CSI to adjustthe parameters for its MIMO data transmission. The CSI values may dependon the phase and amplitude relationships between the channels of antennaports associated with one or more beams and/or polarizations. Forexample, these relationships may change due to certain events orconditions, such as: (a) channel fading and time varying degrees ofchannel blockage; and/or (b) UE activities (e.g., UE beam refinement orswitching of UE antenna subarrays). The UE may detect channel fading orvariations in channel blocking from the reception of periodic downlinkreference signals (RSs), such as synchronization signal blocks (SSB) orperiodic CSI-RSs for beam management. The UE may also use these signalsfor refinement of the beams of the UE, and to determine whether toswitch to a different antenna subarray. The UE may be configured toconduct these actions without any trigger or further support from thebase station.

If the previously described events and/or conditions (e.g., (a) and/or(b)) occur with respect to at least one beam of a beam pair link that isincluded in a pool of beam pair links for data transmission, a newCSI-RS should follow such events and/or conditions to enable adjustmentof MIMO transmission parameters. If a new CSI-RS does not follow suchevents and/or conditions, a UE may not be able to reap the benefit of abeam refinement operation or a subarray switching operation performed bythe UE. Moreover, any MIMO transmissions from the UE subsequent to theevents and/or conditions may operate at a suboptimal level or may evenfail.

In conventional systems, the base station cannot detect when thepreviously described events and/or conditions (e.g., (a) and/or (b))occur. Furthermore, in current NR specifications, the base station mayeither transmit a CSI-RS for channel acquisition after several failedMIMO transmissions or the scheduling entity may schedule frequent CSI-RStransmissions. Both of these alternatives for the base station areinefficient.

Uplink Communications

Situations similar to those discussed above with respect to downlinkdata transmissions may also occur for uplink data transmissions.According to the reciprocity theorem, the pathloss of a beam pair linkis the same regardless of whether it is used for uplink datatransmissions or downlink data transmissions. Therefore, useful beampair links that have already been discovered for the downlink may beimplemented for the uplink Accordingly, in one example, a base stationmay obtain a beam pair link (BPL) to be used for an uplink datatransmission by referring to a downlink reference signal (RS). Forexample, the same beam pair link that was previously used by the basestation to transmit a downlink reference signal (RS) may be used by thebase station to receive uplink data transmissions. This is possiblebecause, for a selected beam pair link, signals in uplink datatransmissions from a UE may propagate along similar paths (but in areverse direction) as signals in downlink data transmissions from a basestation. For example, to receive an uplink data transmission, the basestation may use a reception beam (also referred to as an Rx-beam) thathas the same directivity pattern as a transmission beam (also referredto as an Tx-beam) previously used by the base station to transmit adownlink RS. Likewise, the UE may have already determined a receptionbeam suitable to receive the downlink RS from the base station.Accordingly, for an uplink data transmission, the UE may form atransmission beam that has the same (or similar) directivity pattern asthe reception beam. Therefore, in accordance with the previouslydescribed reciprocity theorem, an improvement of the downlink through areception beam refinement performed by a UE, or a reception antennasubarray switching performed by the UE, may automatically translate tothe uplink if the UE refines its transmission beam or switches itstransmission subarray accordingly. Also, any channel fading and/orchannel blocking discovered in the downlink may affect the uplink in thesame manner. Thus, channel fading and/or channel blocking in thedownlink, reception beam refinements performed by the UE, or antennasubarray switching operations performed by the UE will also affect theMIMO uplink data transmission.

For an uplink MIMO transmission, the base station may schedule the UE totransmit a Sounding Reference Signal (SRS) to enable the base station toobtain the parameters (modulation and coding scheme (MCS), number oflayers, precoding matrix) for the uplink MIMO transmission. Therefore,the occurrence of events and/or conditions, such as channel fading,channel blocking, beam refinement operations performed by the UE, and/orantenna subarray switching operations performed by the UE, should befollowed by a transmission of an SRS from the UE if the affected beampair link is included in the pool of beam pair links for an uplink datatransmission. If an SRS from the UE does not follow such events and/orconditions, a UE may not reap the benefit of a beam refinement operationor antenna subarray switching operation performed by the UE. Moreover,any MIMO transmissions from the UE subsequent to the events and/orconditions may operate at a suboptimal level or may even fail.

As explained herein, in conventional systems, a base station cannotdetect when the previously described events and/or conditions (e.g., (a)and/or (b)) occur. Furthermore, in current NR specifications, a basestation may either schedule a UE to transmit an SRS after several faileduplink MIMO transmissions or the base station may schedule frequent SRStransmissions. Both of these alternatives for the base station areinefficient.

Requests from a Scheduled Entity for Reference Signal Transmissions

In an aspect of the disclosure, a scheduled entity (e.g., scheduledentity 500) may determine whether a CSI-RS transmission (e.g., forchannel acquisition) from the scheduling entity (e.g., scheduling entity400) is needed, or whether an SRS transmission (e.g., for channelacquisition) from the scheduled entity is needed, based on one or moreevents and/or conditions. For example, the scheduled entity may make thedetermination as to whether a CSI-RS transmission or an SRS transmissionis needed based on one or more events and/or conditions, such as: (1)measurements obtained by the scheduled entity; (2) any beam refinementoperations performed by the scheduled entity; and/or (3) any antennasubarray switching operations performed by the scheduled entity. If thescheduled entity determines that a CSI-RS transmission or an SRStransmission is needed, the scheduled entity may transmit a request forthe CSI-RS transmission or the SRS transmission to the schedulingentity. In an aspect of the disclosure, the scheduled entity maytransmit the request for the CSI-RS transmission or the SRS transmissionif one or more beams of the scheduled entity involved in the one or moreevents and/or conditions (e.g., events and/or conditions (1), (2) and/or(3)) are included in the pool of scheduled entity beams for downlink oruplink data transmission, respectively.

In an aspect of the disclosure, the request for transmission of areference signal (e.g., CSI-RS or SRS) transmitted from the scheduledentity may include an indication of the beam pair link(s) associatedwith the scheduled entity beams involved in in the one or more eventsand/or conditions (e.g., events and/or conditions (1), (2) and/or (3)).Such indication of the beam pair link(s) may be achieved by transmittinga spatial quasi co-location (QCL) indication. If the pool of QCLindications for data transmission consists of only one element, the QCLindication may not be needed. For example, the spatial QCL indicationmay enable the scheduling entity to transmit a CSI-RS that is beamformedin a direction of the beam pair link indicated in the spatial QCLindication. As another example, the spatial QCL indication may enablethe scheduling entity to schedule an SRS transmission from the scheduledentity according to the spatial QCL indication, such that the scheduledentity transmits an SRS that is beamformed in a direction of the beampair link indicated in the spatial QCL indication.

In some aspects of the disclosure, the request transmitted from thescheduled entity (e.g., scheduled entity 500) may further include aquality metric that enables the scheduling entity to determine whetherto transmit a CSI-RS or schedule a transmission of an SRS. For example,the quality metric may estimate the amount of improvement that can beexpected from the transmission of CSI-RS or SRS, and the followingrecalculation of the MIMO transmission parameters. For example, theamount of improvement may be indicated as a pathloss improvement withrespect to a channel and may be expressed in decibels (dB). Accordingly,in such example, the scheduling entity may determine to transmit aCSI-RS (or schedule transmission of an SRS) if the amount of improvement(e.g., quality metric) exceeds a threshold. Therefore, the scheduledentity may be configured to use this metric to determine whether theCSI-RS or SRS transmission is worthwhile given any buffered datatraffic. In some aspects of the disclosure, the scheduled entity maytransmit the request in a message on a physical uplink shared channel(PUSCH) or a physical uplink control channel (PUCCH), or may transmitthe request as part of a downlink beam report.

FIG. 6 is a signal flow diagram in accordance with some aspects of thedisclosure. It should be understood that the operations shown withdashed lines in FIG. 6 represent optional operations. FIG. 6 includes ascheduled entity 602 and a scheduling entity 604. For example, thescheduled entity 602 may correspond to the scheduled entity 500 in FIG.5 and the scheduling entity 604 may correspond to the scheduling entity400 in FIG. 4.

As shown in FIG. 6, the scheduled entity 602 may detect channel fadingand/or channel blocking 606. As further shown in FIG. 6, the scheduledentity 602 may perform a beam refinement operation and/or may switch anantenna subarray 608. The scheduled entity 602 may transmit a message610 that includes a reference signal request. In some aspects, thescheduled entity 602 may transmit the message 610 in response toperforming operation 606 and/or 608.

The scheduling entity 604 may transmit a reference signal 612 (e.g., aCSI-RS) in response to the reference signal request. The scheduledentity 602 may obtain channel state information 614 using the referencesignal 612 and may transmit a report 616 that includes the channel stateinformation. The scheduling entity 604 may obtain transmissionparameters 618 (e.g., MCS, MIMO precoding matrix, etc.) based on thechannel state information. The scheduling entity 604 may then transmitdownlink (DL) data 620 using a MIMO transmission based on thetransmission parameters.

In one example, the reference signal request in the message 610 mayinclude a request for a CSI-RS with a QCL indication Q. The schedulingentity 604 may transmit a reference signal 612 (e.g., a CSI-RS) with abeam compatible with the QCL indication Q. The scheduled entity 602 mayrefine (e.g., improve) its receive beam and may measure a receive power,such as a reference signal received power (RSRP) (also referred to as aphysical layer RSRP or a Layer 1 RSRP (L1-RSRP)), using the refinedreceive beam. Since the scheduled entity 602 may measure the receivepower using the refined receive beam, the scheduled entity 602 maymeasure a more accurate (e.g., a higher RSRP) receive power. Thescheduled entity 602 may include the more accurate receive power (e.g.,RSRP) in the report 616. The scheduled entity 602 may use the refinedreceive beam whenever the scheduling entity 604 transmits a DL channelor signal (e.g., DL data 620) with the QCL indication Q. In thisexample, it should be noted that the scheduled entity 602 may notexplicitly indicate the refined receive beam in the report 616. In someaspects of the disclosure, the scheduled entity 602 may apply theresults of its measurements to future downlink transmissions from thescheduling entity 604. In some aspects of the disclosure, the schedulingentity 604 may use the more accurate receive power in the report 616 toadjust its transmit power for future downlink data transmissions withthe QCL indication Q.

In another example, the scheduling entity 604 may transmit the referencesignal 612 (e.g., CSI-RS) with different beams in different symbols.These different beams may have different QCL indications. The scheduledentity 602 may measure the different beams and may determine the bestbeam (e.g., the beam with the highest receive power) based on themeasurements. The scheduled entity 602 may indicate the best beam andthe best (e.g., highest) receive power in the report 616. In someaspects of the disclosure, the scheduled entity 602 may optimize itsreceive beam. The scheduling entity 604 may proceed to use the best beamindicated in the report 616 and the scheduled entity 602 may use itsmatching best beam when receiving future downlink transmissions from thescheduling entity 604. In this example, the scheduling entity 604 maytransmit the previously described different beams (e.g., CSI-RS) as partof a beam sweep. In other examples, the scheduled entity 602 mayestimate the amount of improvement (e.g., the amount of increase in theRSRP) and may include the amount of improvement in the message 610. Inthese examples, the scheduling entity 604 may transmit the referencesignal 612 (e.g., CSI-RS) with a constant (non-sweeping) beam.

FIG. 7 is a signal flow diagram in accordance with some aspects of thedisclosure. It should be understood that the operations shown withdashed lines in FIG. 7 represent optional operations. FIG. 7 includes ascheduled entity 702 and a scheduling entity 704. For example, thescheduled entity 702 may correspond to the scheduled entity 500 in FIG.5 and the scheduling entity 704 may correspond to the scheduling entity400 in FIG. 4.

As shown in FIG. 7, the scheduled entity 702 may detect channel fadingand/or channel blocking 706. As further shown in FIG. 7, the scheduledentity 702 may perform a beam refinement operation and/or may switch anantenna subarray 708. The scheduled entity 702 may transmit a message710 that includes a reference signal scheduling request. In someaspects, the scheduled entity 702 may transmit the message 710 inresponse to performing operation 706 and/or 708.

The scheduling entity 704 may transmit a message 712 including anassignment of resources (e.g., time-frequency resources) in response tothe reference signal scheduling request. The scheduled entity 702 maytransmit a reference signal 714 (e.g., an SRS) using the assignedresources. The scheduling entity 704 may obtain channel stateinformation 716 using the reference signal 714 and may obtaintransmission parameters 718 (e.g., MCS, MIMO precoding matrix, etc.)based on the channel state information. The scheduling entity 704 maythen transmit uplink (UL) data transmission scheduling information 720(for an uplink MIMO transmission) to the scheduled entity 702 based onthe transmission parameters.

In some aspects of the disclosure, the message 712 may schedule thescheduled entity 702 to transmit the reference signal 714 (e.g., an SRS)with different beams (e.g., different QCL indications). The schedulingentity 704 may then determine the beam that produces the highest receivepower at the scheduling entity 704. The scheduling entity 704 may thenschedule the scheduled entity 702 (e.g., via the data transmissionscheduling information 720) to transmit UL data or UL control with thebeam that produces the highest receive power.

In some aspects of the disclosure, the scheduling entity 704 mayschedule the scheduled entity 702 to transmit the reference signal 714(e.g., an SRS) with different antenna ports. The scheduling entity 704may measure the reference signal 714 transmitted from the differentantenna ports and may determine which antenna port (or which subset ofantenna ports) provides the best UL MIMO transmission. The schedulingentity 704 may then schedule the scheduled entity 702 (e.g., via thedata transmission scheduling information 720) with the identified subsetof antenna ports for future UL transmissions.

FIG. 8 is a flow chart illustrating an exemplary process 800 inaccordance with some aspects of the present disclosure. As describedbelow, some or all illustrated features may be omitted in a particularimplementation within the scope of the present disclosure, and someillustrated features may not be required for implementation of allembodiments. In some examples, the process 800 may be carried out by thescheduled entity 500 illustrated in FIG. 5. In some examples, theprocess 800 may be carried out by any suitable apparatus or means forcarrying out the functions or algorithm described below. It should beunderstood that the blocks indicated with dashed lines representoptional blocks.

At block 802, the scheduled entity estimates an amount of improvement ina quality of a downlink data transmission to be gained from atransmission of a reference signal.

At block 804, the scheduled entity transmits a message that requests ascheduling entity to transmit at least one reference signal. In anaspect of the disclosure, the at least one reference signal may be aCSI-RS. In an aspect of the disclosure, the scheduled entity transmitsthe message if the scheduled entity has refined a reception beam for atleast one beam pair link, if the scheduled entity has switched areception subarray for at least one beam pair link, or if the scheduledentity has detected a change of a channel of at least one beam pair linkIn such aspect, the at least one beam pair link is configured fordownlink traffic. In an aspect of the disclosure, the message includes adownlink beam report, and a request for transmission of the at least onereference signal is included in the downlink beam report. In an aspectof the disclosure, the message may include one or more spatial QCLindications. In such aspect, the at least one reference signal may beobtained using one or more reception directivity patterns, at least oneof the one or more reception directivity patterns being compatible withat least one of the spatial QCL indications. In an aspect, the estimatedamount of improvement is included in the message.

At block 806, the scheduled entity obtains channel state informationbased on the at least one reference signal. In an aspect of thedisclosure, the scheduled entity may obtain the channel stateinformation by obtaining one or more measurements for a channel usingthe at least one reference signal, and determining the channel stateinformation based on the one or more measurements.

At block 808, the scheduled entity transmits a report that includes thechannel state information.

FIG. 9 is a flow chart illustrating an exemplary process 900 inaccordance with some aspects of the present disclosure. As describedbelow, some or all illustrated features may be omitted in a particularimplementation within the scope of the present disclosure, and someillustrated features may not be required for implementation of allembodiments. In some examples, the process 900 may be carried out by thescheduled entity 500 illustrated in FIG. 5. In some examples, theprocess 900 may be carried out by any suitable apparatus or means forcarrying out the functions or algorithm described below. It should beunderstood that the blocks indicated with dashed lines representoptional blocks.

At block 902, the scheduled entity estimates an amount of improvement ina quality of an uplink data transmission to be gained from thetransmission of a reference signal.

At block 904, the scheduled entity transmits a message that requests ascheduling entity to schedule a reference signal transmission for thescheduled entity. In an aspect of the disclosure, the at least onereference signal is an SRS. In an aspect of the disclosure, thescheduled entity transmits the message if the scheduled entity hasrefined a reception beam for at least one beam pair link, if thescheduled entity has switched a reception subarray for at least one beampair link, or if the scheduled entity has detected a change of a channelof at least one beam pair link, and wherein at least one spatial QCLindication for uplink traffic refers to the at least one beam pair linkIn an aspect of the disclosure, the message includes a downlink beamreport, and a request for transmission of the reference signal (e.g.,SRS) is included in the downlink beam report. In an aspect, theestimated amount of improvement is included in the message.

At block 906, the scheduled entity obtains an assignment of resourcesfor transmission of the reference signal in response to the message. Inan aspect of the disclosure, the assignment of resources includes atleast time-frequency resources. In an aspect of the disclosure, themessage includes one or more spatial QCL indications, the assignment ofresources specifies at least one of the one or more spatial QCLindications, and the scheduled entity transmits the at least onereference signal using one or more transmission directivity patternscompatible with the specified at least one of the one or more spatialQCL indications.

At block 908, the scheduled entity transmits the reference signal basedon the assignment of resources.

FIG. 10 is a flow chart illustrating an exemplary process 1000 inaccordance with some aspects of the present disclosure. As describedbelow, some or all illustrated features may be omitted in a particularimplementation within the scope of the present disclosure, and someillustrated features may not be required for implementation of allembodiments. In some examples, the process 1000 may be carried out bythe scheduling entity 400 illustrated in FIG. 4. In some examples, theprocess 1000 may be carried out by any suitable apparatus or means forcarrying out the functions or algorithm described below. It should beunderstood that the blocks indicated with dashed lines representoptional blocks.

At block 1002, the scheduling entity obtains a message that requests thescheduling entity to transmit at least one reference signal. In anaspect of the disclosure, the at least one reference signal is a CSI-RS.

At block 1004, the scheduling entity transmits the at least onereference signal to a scheduled entity in response to the message. In anaspect of the disclosure, the message includes one or more spatial QCLindications, and the scheduling entity transmits the at least onereference signal using one or more transmission directivity patterns, atleast one of the one or more transmission directivity patterns beingcompatible with at least one of the spatial QCL indications.

At block 1006, the scheduling entity obtains a report including channelstate information from the scheduled entity, where the channel stateinformation is based on the at least one reference signal.

At block 1008, the scheduling entity transmits data based on at leastthe channel state information. In an aspect of the disclosure, the datais transmitted in a multiple-input multiple-output (MIMO) transmissionmode using a modulation and coding scheme (MCS) that is determined usingthe channel state information.

FIG. 11 is a flow chart illustrating an exemplary process 1100 inaccordance with some aspects of the present disclosure. As describedbelow, some or all illustrated features may be omitted in a particularimplementation within the scope of the present disclosure, and someillustrated features may not be required for implementation of allembodiments. In some examples, the process 1100 may be carried out bythe scheduling entity 400 illustrated in FIG. 4. In some examples, theprocess 1100 may be carried out by any suitable apparatus or means forcarrying out the functions or algorithm described below. It should beunderstood that the blocks indicated with dashed lines representoptional blocks.

At block 1102, the scheduling entity obtains a message that requests thescheduling entity to schedule a reference signal transmission for ascheduled entity. In an aspect of the disclosure, the reference signalis a sounding reference signal (SRS).

At block 1104, the scheduling entity transmits a first assignment ofresources to the scheduled entity for transmission of the referencesignal in response to the message. In an aspect of the disclosure, themessage includes one or more spatial QCL indications, wherein the firstassignment of resources indicates that the reference signal is to betransmitted using one or more transmission directivity patterns, atleast one of the one or more transmission directivity patterns beingcompatible with at least one of the one or more spatial QCL indications.

At block 1106, the scheduling entity obtains at least one referencesignal from the scheduled entity.

At block 1108, the scheduling entity obtains channel state informationbased on the at least one reference signal from the scheduled entity.

At block 1110, the scheduling entity transmits a second assignment ofresources to the scheduled entity for an uplink data transmission in aMIMO transmission mode, wherein the resources, the modulation and codingscheme, and other MIMO parameters are assigned based on the channelstate information.

In one configuration, the apparatus 400 for wireless communicationincludes means for transmitting a message that requests a schedulingentity to transmit at least one reference signal, means for obtainingchannel state information based on the at least one reference signal,means for transmitting a report that includes the channel stateinformation, means for estimating an amount of improvement in a qualityof an uplink data transmission to be gained from the transmission of thereference signal, wherein the estimated amount of improvement isincluded in the message, means for transmitting a message that requestsa scheduling entity to schedule a reference signal transmission for thescheduled entity, means for obtaining an assignment of resources fortransmission of the reference signal in response to the message, meansfor transmitting at least one reference signal based on the assignmentof resources. In an aspect, the means for obtaining the channel stateinformation based on the at least one reference signal is configured toobtain one or more measurements for a channel using the at least onereference signal, and determine the channel state information based onthe one or more measurements. In one aspect, the aforementioned meansmay be the processor(s) 404 configured to perform the functions recitedby the aforementioned means. In another aspect, the aforementioned meansmay be a circuit or any apparatus configured to perform the functionsrecited by the aforementioned means.

Of course, in the above examples, the circuitry included in theprocessor 404 is merely provided as an example, and other means forcarrying out the described functions may be included within variousaspects of the present disclosure, including but not limited to theinstructions stored in the computer-readable storage medium 406, or anyother suitable apparatus or means described in any one of the FIGS. 1-3,6 and/or 7, and utilizing, for example, the processes and/or algorithmsdescribed herein in relation to FIGS. 8 and/or 9.

In one configuration, the apparatus 500 for wireless communicationincludes means for obtaining a message that requests the schedulingentity to transmit at least one reference signal, means for transmittingthe at least one reference signal to a scheduled entity in response tothe message, means for obtaining a report including channel stateinformation from the scheduled entity, wherein the channel stateinformation is based on the at least one reference signal, means fortransmitting data based on at least the channel state information, meansfor obtaining a message that requests the scheduling entity to schedulea reference signal transmission for a scheduled entity, means fortransmitting a first assignment of resources to the scheduled entity fortransmission of the reference signal in response to the message, meansfor obtaining the at least one reference signal from the scheduledentity, means for obtaining channel state information based on the atleast one reference signal from the scheduled entity, and means fortransmitting a second assignment of resources to the scheduled entityfor an uplink data transmission in a multiple-input multiple-output(MIMO) transmission mode, wherein the resources are assigned based onthe channel state information. In one aspect, the aforementioned meansmay be the processor(s) 504 configured to perform the functions recitedby the aforementioned means. In another aspect, the aforementioned meansmay be a circuit or any apparatus configured to perform the functionsrecited by the aforementioned means.

Of course, in the above examples, the circuitry included in theprocessor 504 is merely provided as an example, and other means forcarrying out the described functions may be included within variousaspects of the present disclosure, including but not limited to theinstructions stored in the computer-readable storage medium 506, or anyother suitable apparatus or means described in any one of the FIGS. 1-3,6 and/or 7, and utilizing, for example, the processes and/or algorithmsdescribed herein in relation to FIGS. 10 and/or 11.

Several aspects of a wireless communication network have been presentedwith reference to an exemplary implementation. As those skilled in theart will readily appreciate, various aspects described throughout thisdisclosure may be extended to other telecommunication systems, networkarchitectures and communication standards.

By way of example, various aspects may be implemented within othersystems defined by 3GPP, such as Long-Term Evolution (LTE), the EvolvedPacket System (EPS), the Universal Mobile Telecommunication System(UMTS), and/or the Global System for Mobile (GSM). Various aspects mayalso be extended to systems defined by the 3rd Generation PartnershipProject 2 (3GPP2), such as CDMA2000 and/or Evolution-Data Optimized(EV-DO). Other examples may be implemented within systems employing IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB),Bluetooth, and/or other suitable systems. The actual telecommunicationstandard, network architecture, and/or communication standard employedwill depend on the specific application and the overall designconstraints imposed on the system.

Within the present disclosure, the word “exemplary” is used to mean“serving as an example, instance, or illustration.” Any implementationor aspect described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other aspects of thedisclosure. Likewise, the term “aspects” does not require that allaspects of the disclosure include the discussed feature, advantage ormode of operation. The term “coupled” is used herein to refer to thedirect or indirect coupling between two objects. For example, if objectA physically touches object B, and object B touches object C, thenobjects A and C may still be considered coupled to one another—even ifthey do not directly physically touch each other. For instance, a firstobject may be coupled to a second object even though the first object isnever directly physically in contact with the second object. The terms“circuit” and “circuitry” are used broadly, and intended to include bothhardware implementations of electrical devices and conductors that, whenconnected and configured, enable the performance of the functionsdescribed in the present disclosure, without limitation as to the typeof electronic circuits, as well as software implementations ofinformation and instructions that, when executed by a processor, enablethe performance of the functions described in the present disclosure. Asused herein, the term “obtaining” may include one or more actionsincluding, but not limited to, receiving, generating, determining, orany combination thereof.

One or more of the components, steps, features and/or functionsillustrated in FIGS. 1-11 may be rearranged and/or combined into asingle component, step, feature or function or embodied in severalcomponents, steps, or functions. Additional elements, components, steps,and/or functions may also be added without departing from novel featuresdisclosed herein. The apparatus, devices, and/or components illustratedin FIGS. 1-11 may be configured to perform one or more of the methods,features, or steps described herein. The novel algorithms describedherein may also be efficiently implemented in software and/or embeddedin hardware.

It is to be understood that the specific order or hierarchy of steps inthe methods disclosed is an illustration of exemplary processes. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the methods may be rearranged. The accompanyingmethod claims present elements of the various steps in a sample order,and are not meant to be limited to the specific order or hierarchypresented unless specifically recited therein.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, band c. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. § 112(f) unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

What is claimed is:
 1. A method of wireless communication, comprising:transmitting, from a scheduled entity, a message that requests ascheduling entity to schedule a reference signal transmission for thescheduled entity; obtaining, at the scheduled entity, an assignment ofresources for transmission of the reference signal in response to themessage; and transmitting, from the scheduled entity, the referencesignal based on the assignment of resources.
 2. The method of claim 1,wherein the reference signal is a sounding reference signal (SRS). 3.The method of claim 1, wherein the assignment of resources includes atleast time-frequency resources.
 4. The method of claim 1, wherein themessage includes one or more spatial quasi co-location (QCL)indications, wherein the assignment of resources specifies at least oneof the one or more spatial QCL indications, and wherein the scheduledentity transmits the reference signal using one or more transmissiondirectivity patterns compatible with the specified at least one of theone or more spatial QCL indications.
 5. The method of claim 1, whereinthe scheduled entity transmits the message if the scheduled entity hasrefined a reception beam for at least one beam pair link, if thescheduled entity has switched a reception subarray for at least one beampair link, or if the scheduled entity has detected a change of a channelof at least one beam pair link, and wherein at least one spatial quasico-location (QCL) indication for uplink traffic refers to the at leastone beam pair link
 6. The method of claim 1, further comprising:estimating an amount of improvement in a quality of an uplink datatransmission to be gained from the transmission of the reference signal,wherein the estimated amount of improvement is included in the message.7. The method of claim 1, wherein the message includes a downlink beamreport, and wherein a request for transmission of the reference signalis included in the downlink beam report.
 8. An apparatus for wirelesscommunication, comprising: at least one processor; a transceivercommunicatively coupled to the at least one processor; and a memorycommunicatively coupled to the at least one processor, wherein the atleast one processor is configured to: transmit a message that requests ascheduling entity to schedule a reference signal transmission for theapparatus; obtain an assignment of resources for transmission of thereference signal in response to the message; and transmit the referencesignal based on the assignment of resources.
 9. The apparatus of claim8, wherein the reference signal is a sounding reference signal (SRS).10. The apparatus of claim 8, wherein the assignment of resourcesincludes at least time-frequency resources.
 11. The apparatus of claim8, wherein the message includes one or more spatial quasi co-location(QCL) indications, wherein the assignment of resources specifies atleast one of the one or more spatial QCL indications, and wherein theapparatus transmits the reference signal using one or more transmissiondirectivity patterns compatible with the specified at least one of theone or more spatial QCL indications.
 12. The apparatus of claim 8,wherein the apparatus transmits the message if the apparatus has refineda reception beam for at least one beam pair link, if the apparatus hasswitched a reception subarray for at least one beam pair link, or if theapparatus has detected a change of a channel of at least one beam pairlink, and wherein at least one spatial quasi co-location (QCL)indication for uplink traffic refers to the at least one beam pair link13. The apparatus of claim 8, further comprising: estimating an amountof improvement in a quality of an uplink data transmission to be gainedfrom the transmission of the reference signal, wherein the estimatedamount of improvement is included in the message.
 14. The apparatus ofclaim 8, wherein the message includes a downlink beam report, andwherein a request for transmission of the reference signal is includedin the downlink beam report.
 15. A method of wireless communication,comprising: obtaining, at a scheduling entity, a message that requeststhe scheduling entity to schedule a reference signal transmission for ascheduled entity; transmitting, from the scheduling entity, a firstassignment of resources to the scheduled entity for transmission of thereference signal in response to the message; and obtaining, at thescheduling entity, at least one reference signal from the scheduledentity.
 16. The method of claim 15, further comprising: obtaining, atthe scheduling entity, channel state information based on the at leastone reference signal from the scheduled entity; and transmitting, fromthe scheduling entity, a second assignment of resources to the scheduledentity for an uplink data transmission in a multiple-inputmultiple-output (MIMO) transmission mode, wherein the resources, themodulation and coding scheme, and other MIMO parameters are assignedbased on the channel state information.
 17. The method of claim 15,wherein the message includes one or more spatial quasi co-location (QCL)indications, wherein the first assignment of resources indicates thatthe at least one reference signal is to be transmitted using one or moretransmission directivity patterns, at least one of the one or moretransmission directivity patterns being compatible with at least one ofthe one or more spatial QCL indications.
 18. The method of claim 15,wherein the at least one reference signal is a sounding reference signal(SRS).